When it comes to social networking, “there are an incredible number of people who want to be known as influential,” says Eric Wheeler, CEO of the New York City startup 33Across. Of course, there are also plenty of people–advertisers, namely–who want to know who the influential people are. Wheeler would cater to both. A number of companies try to help target ads based on users’ behavior; a visitor to Cars.com, for example, might see Ford ads. In June, 33Across announced its first partnership with a social-networking site–Meebo–to build anonymous profiles of users’ actual influence.

The profiles are drawn from the usual sources–self-provided information and Web browsing history–as well as from details on users’ networks and their propensity to communicate. The goal: to find gossipy influencers who will be the “viral promoters” of, say, a new product, says Christine Herron of First Round Capital, an investor. “All this data can be used to understand an incredible amount of detail about a person’s influence,” she says.

Mainly, “it allows advertisers to be much smarter in how they deliver a message,” says Wheeler, formerly CEO of ad agency Neo@Ogilvy North America. In exchange for giving 33Across nonprivate user data, social-networking sites get a piece of the resulting ad revenue. Users could benefit, too, since the social-­networking site could share the data with them. Measures of influence might be important to bloggers, among others. 33Across plans a full launch in September.